The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars

R. J. de Rosa, J. Bulger, J. Patience, B. Leland, B. Macintosh, A. Schneider, I. Song, C. Marois, J. R. Graham, M. Bessell, R. Doyon

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


With an adaptive optics imaging survey of 148 B6-A7 stars, we have tested the hypothesis that unresolved lower mass companions are the source of the unexpected X-ray detections of stars in this spectral type range. The sample is composed of 63 stars detected in X-rays within the ROSAT All Sky Survey and 85 stars that form a control sample; both subsets have the same restricted distribution of spectral type, age, X-ray sensitivity and separation coverage. A total of 68 companion candidates are resolved with separations ranging from 0.3 to 26.2 arcsec, with 23 new detections. The multiple star frequency of the X-ray sample based on companions resolved within the ROSAT error ellipse is found to be 43+6-6 per cent. The corresponding control sample multiple star frequency is three times lower at 12+4-3 per cent - a difference of 31 ± 7 per cent. These results are presented in the first of a series of papers based on our Volume-limited A-Star (VAST) survey - a comprehensive study of the multiplicity of A-type stars.

Original languageEnglish (US)
Pages (from-to)854-866
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jul 2011
Externally publishedYes


  • Binaries: general
  • Stars: early-type
  • Stars: imaging
  • Techniques: high angular resolution
  • X-rays: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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